Data storage devices are subject to data loss from a variety of causes, such as disk failure, unintentional deletion, malicious software attacks, or natural disaster. A common practice to guard against data loss is to create backup copies of important data and store them at a remote storage location. In the event of data loss or corruption, the backup copies are used to restore the lost or corrupted data to a previous state.
Backup storage systems typically allow client systems to restore data within a fixed window of time. The storage system can automatically back up the data at preset intervals of time or immediately log changes to the client system. In enterprise organizations, the large quantity of information and frequent backup intervals often necessitate a great amount of overhead and storage resources.
To reduce costs and simplify manageability, backup resources can be shared between multiple client systems. In one approach, to prevent one or more clients from consuming too many storage resources, each client is assigned a storage quota. The quota acts as a maximum limit, which restricts the amount of data that each client may store. If a particular client system has reached its quota, the client system is required to delete its old backup data before it can store any new backup data.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.